In the construction of simple structures such as a house or a light commercial building, a number of different types of foundation designs may be utilized. Some of the most commonly used designs include (a) a concrete slab, over which the structure is built, (b) a subgrade basement, over which the structure is built, (c) post-and-pillar construction, where vertical posts rise from footings, and the posts are used to support girders, upon which the building is constructed, and (d) stem wall construction, where a poured vertical concrete wall forms the support for the structure.
In the popular stem wall construction technique, concrete forms are positioned at desired locations on the ground. Then, concrete is poured into these forms to (a) provide a footing, and (b) to form a vertical stem wall. When the concrete sets in the wall forms, there results a vertical concrete stem wall. A frame building is then constructed above the vertical stem wall. A crawl space is provided underneath the frame building; the crawl space normally provides a minimum of about eighteen (18) inches of vertical space between the ground and the bottom of the frame structure. The crawl space is also an air ventilation space. This is important since without air circulation underneath the frame building, there may be damage, such as dry rot, due to presence of moisture or condensation beneath the frame structure. However, in order to have an air ventilation space, it is necessary to have a means for passage of air through the concrete wall. Our invention is directed to a novel ventilation apparatus for placement in vertical concrete walls to allow air to pass therethrough.
Generally, there have been developed a wide variety of devices which may be utilized to provide ventilation means in walls. With respect to stem type walls, number of such devices are known. In the patent literature, U.K Patent No. 8210, issued Mar. 5, 1898 to Tiltman for IMPROVEMENTS IN VENTILATORS, U.S. Pat. No. 3,220,079 issued Nov. 30, 1965 to Aggeson for FOUNDATION VENT, and U.S. Pat. No. 4,026,082 issued May 31, 1977 to Crofoot for VENT FRAMES, are the closest utility patents of which we are aware. Other important art of which we are aware includes our own designs: U.S. Pat. No. Des. 258,985 issued Apr. 21, 1981 to Peirce et al. for VENTILATOR SECTION; U.S. Pat. No. Des. 259,736 issued Jun. 30, 1981 to Peirce et al. for VENTILATOR SECTION; U.S. Pat. No. Des. 260,117 issued Aug. 4, 1981 to Peirce et al. for VENTILATOR SECTION; U.S. Pat. No. Des. 269,293 issued Jul. 7, 1983 to Peirce et al. for VENTILATOR; and U.S. Pat. No. Des. 269,700 issued Jul. 12, 1983 to Peirce et al. for VENTILATOR.
In so far as we are aware, the patent documents identified in the proceeding paragraph, with the exception of Tiltman, disclose ventilators with multi-piece construction. The Tiltman patent discloses a cast iron wall sleeve for use in a ventilator device, but does not address the construction of a low cost plastic ventilator, nor does Tiltman suggest the desirability of varying the cross-sectional area of the ventilator from front to back. Although our multi-part ventilators, shown in U.S. Pat. No. Des. 269,293 and Des. 269,700, disclose ventilators which upon first impression are similar in appearance to the present invention, nevertheless they did not teach the advantages of one-piece molded construction of according to our present invention. In order to reduce fabrication costs, to improve ventilator strength, and to reduce deformation during the concrete pouring process, there exists a continuing need in the art for an improved ventilator design, and for an improved method of fabricating a ventilator.